The present invention relates to retroviral protease inhibitors and, more particularly, relates to novel compounds, composition and method for inhibiting retroviral proteases, such as human immunodeficiency virus (HIV) protease. This invention, in particular, relates to sulfonylalkanoylamino hydroxyethylamine sulfonamide protease inhibitor compounds, composition and method for inhibiting retroviral proteases, prophylactically preventing retroviral infection or the spread of a retrovirus, and treatment of a retroviral infection, e.g., an HIV infection. The subject invention also relates to processes for making such compounds as well as to intermediates useful in such processes.
During the replication cycle of retroviruses, gag and gag-pol gene transcription products are translated as proteins. These proteins are subsequently processed by a virally encoded protease (or proteinase) to yield viral enzymes and structural proteins of the virus core. Most commonly, the gag precursor proteins are processed into the core proteins and the pol precursor proteins are processed into the viral enzymes, e.g., reverse transcriptase and retroviral protease. It has been shown that correct processing of the precursor proteins by the retroviral protease is necessary for assembly of infectious virons. For example, it has been shown that frameshift mutations in the protease region of the pol gene of HIV prevents processing of the gag precursor protein. It has also been shown through site-directed mutagenesis of an aspartic acid residue in the HIV protease active site that processing of the gag precursor protein is prevented. Thus, attempts have been made to inhibit viral replication by inhibiting the action of retroviral proteases.
Retroviral protease inhibition typically involves a transition-state mimetic whereby the retroviral protease is exposed to a mimetic compound which binds (typically in a reversible manner) to the enzyme in competition with the gag and gag-pol proteins to thereby inhibit specific processing of structural proteins and the release of retroviral protease itself. In this manner, retroviral replication proteases can be effectively inhibited.
Several classes of compounds have been proposed, particularly for inhibition of proteases, such as for inhibition of HIV protease. WO 92/08701, WO 93/23368, WO 93/23379, WO 94/04493, WO 94/10136 and WO 94/14793 (each of which is incorporated herein by reference in its entirety) for example describe sulfonylalkanoylamino hydroxyethylamine, sulfonylalkanoylamino hydroxyethylurea, sulfonylalkanoylamino hydroxyethyl sulfonamide and sulfonylalkanoylamino hydroxyethylaminosulfonamide isostere containing retroviral protease inhibitors. Other such compounds include hydroxyethylamine isosteres and reduced amide isosteres. See, for example, EP O 346 847; EP O 342,541; Roberts et al, xe2x80x9cRational Design of Peptide-Based Proteinase Inhibitors, xe2x80x9cScience, 248, 358 (1990); and Erickson et al, xe2x80x9cDesign Activity, and 2.8 xc3x85 Crystal Structure of a C2 Symmetric Inhibitor Complexed to HIV-1 Protease,xe2x80x9d Science, 249, 527 (1990). U.S. Pat. No. 5,157,041, WO 94/04491, WO 94/04492, WO 94/05639 and U.S. patent application Ser. No. 08/294,468, filed Aug. 23, 1994, (each of which is incorporated herein by reference in its entirety) for example describe hydroxyethylamine, hydroxyethylurea or hydroxyethyl sulfonamide isostere containing retroviral protease inhibitors.
Several classes of compounds are known to be useful as inhibitors of the proteolytic enzyme renin. See, for example, U.S. Pat. No. 4,599,198; U.K. 2,184,730; G.B. 2,209,752; EP O 264 795; G.B. 2,200,115 and U.S. SIR H725. Of these, G.B. 2,200,115, GB 2,209,752, EP O 264,795, U.S. SIR H725 and U.S. Pat. No. 4,599,198 disclose urea-containing hydroxyethylamine renin inhibitors. EP 468 641 discloses renin inhibitors and intermediates for the preparation of the inhibitors, which include sulfonamide-containing hydroxyethylamine compounds, such as 3-(t-butoxycarbonyl)amino-cyclohexyl-1-(phenylsulfonyl)amino-2(5)-butanol. G.B. 2,200,115 also discloses sulfamoyl-containing hydroxyethylamine renin inhibitors, and EP 0264 795 discloses certain sulfonamide-containing hydroxyethylamine renin inhibitors. However, it is known that, although renin and HIV proteases are both classified as aspartyl proteases, compounds which are effective renin inhibitors generally are not predictive for effective HIV protease inhibition.
The present invention relates to selected retroviral protease inhibitor compounds, analogs and pharmaceutically acceptable salts, esters and prodrugs thereof. The subject compounds are characterized as sulfonylalkanoylamino hydroxyethylamine sulfonamide inhibitor compounds. The invention compounds advantageously inhibit retroviral proteases, such as human immunodeficiency virus (HIV) protease. Therefore, this invention also encompasses pharmaceutical compositions, methods for inhibiting retroviral proteases and methods for treatment or prophylaxis of a retroviral infection, such as an HIV infection. The subject invention also relates to processes for making such compounds as well as to intermediates useful in such processes:
In accordance with the present invention, there is provided a retroviral protease inhibiting compound of the formula: 
or a pharmaceutically acceptable salt, prodrug or ester thereof, wherein n and t each independently represent 0, 1 or 2; preferably n represents 1 and t represents 1 or 2;
R1 represents hydrogen, alkyl, alkenyl, alkynyl, hydroxyalkyl, alkoxyalkyl, cyanoalkyl, xe2x80x94CH2CONH2, xe2x80x94CH2CH2CONH2, xe2x80x94CH2S(O)2NH2, xe2x80x94CH2SCH3, xe2x80x94CH2S(O)CH3 or xe2x80x94CH2S(O)2CH3 radicals; preferably, R1 represents hydrogen, alkyl of 1-5 carbon atoms, alkenyl of 2-5 carbon atoms, alkynyl of 2-5 carbon atoms, hydroxyalkyl of 1-3 carbon atoms, alkoxyalkyl of 1-3 alkyl and 1-3 alkoxy carbon atoms, cyanoalkyl of 1-3 alkyl carbon atoms, xe2x80x94CH2CONH2, xe2x80x94CH2CH2CONH2, xe2x80x94CH2S(O)2NH2, xe2x80x94CH2SCH3, xe2x80x94CH2S(O)CH3 or xe2x80x94CH2S(O)2CH3 radicals; more preferably, R1 represents hydrogen radical, alkyl radical of 1-3 carbon atoms, alkenyl radical of 2-3 carbon atoms, alkynyl radical of 2-3 carbon atoms or cyanomethyl radicals; even more preferably, R1 represents hydrogen, methyl, ethyl or cyanomethyl radicals; yet more preferably, R1 represents methyl or ethyl radicals; and most preferably, R1 represents a methyl radical;
R2 represents alkyl, aralkyl, alkylthioalkyl, arylthioalkyl or cycloalkylalkyl radicals; preferably, R2 represents radicals of alkyl of 1-5 carbon atoms, aralkyl of 1-3 alkyl carbon atoms, alkylthioalkyl of 1-3 alkyl carbon atoms, arylthioalkyl of 1-3 alkyl carbon atoms or cycloalkylalkyl of 1-3 alkyl carbon atoms and 3-6 ring member carbon atoms; more preferably, R2 represents radicals of alkyl of 3-5 carbon atoms, arylmethyl, alkylthioalkyl of 1-3 alkyl carbon atoms, arylthiomethyl or cycloalkylmethyl of 5-6 ring member carbon atoms radicals; even more preferably, R2 represents isobutyl, n-butyl, CH3SCH2CH2xe2x80x94, benzyl, phenylthiomethyl, (2-naphthylthio)methyl, 4-methoxyphenylmethyl, 4-hydroxyphenylmethyl, 4-fluorophenylmethyl or cyclohexylmethyl radicals; even more preferably, R2 represents benzyl, 4-fluorophenylmethyl or cyclohexylmethyl radicals; most preferably, R2 represents benzyl;
R3 represents alkyl, cycloalkyl or cycloalkylalkyl radicals; preferably, R3 represents radicals of alkyl radical of 1-5 carbon atoms, cycloalkyl of 5-8 ring members or cycloalkylmethyl radical of 3-6 ring members; more preferably, R3 represents propyl, isoamyl, isobutyl, butyl, cyclopentylmethyl, cyclohexylmethyl, cyclohexyl or cycloheptyl radicals; more preferably R3 represents isobutyl or cyclopentylmethyl radicals;
R4 represents heteroaryl or heterocyclo radicals; preferably, R4 represents benzo fused 5 to 6 ring member heteroaryl or benzo fused 5 to 6 ring member heterocyclo radicals; or
R4 represents a radical of the formula 
wherein A and B each independently represent O, S, SO or SO2; preferably, A and B each represent O;
R6 represents deuterium, alkyl or halogen radicals; preferably, R6 represents deuterium, alkyl of 1-5 carbon atoms, fluoro or chloro radicals; more preferably R6 represents deuterium, methyl, ethyl, propyl, isopropyl or fluoro radicals;
R7 represents hydrogen, deuterium, alkyl or halogen radicals; preferably, R7 represents hydrogen, deuterium, alkyl of 1-3 carbon atoms, fluoro or chloro radicals; more preferably, R7 represents hydrogen, deuterium, methyl or fluoro radicals; or R6 and R7 each independently represent fluoro or chloro radicals; and preferably, R6 and R7 each represent a fluoro radical; or
R4 represents a radical of the formula 
wherein Z represents O, S or NH; and R9 represents a radical of formula 
wherein Y represents O, S or NH; X represents a bond, O or NR21;
R20 represents hydrogen, alkyl, alkenyl, alkynyl, aralkyl, heteroaralkyl, heterocycloalkyl, aminoalkyl, N-mono-substituted or N,N-disubstituted aminoalkyl wherein said substituents are alkyl or aralkyl radicals, carboxyalkyl, alkoxycarbonylalkyl, cyanoalkyl or hydroxyalkyl radicals; preferably, R20 represents hydrogen, alkyl of 1 to 5 carbon atoms, alkenyl of 2 to 5 carbon atoms, alkynyl of 2 to 5 carbon atoms, aralkyl of 1 to 5 alkyl carbon atoms, heteroaralkyl of 5 to 6 ring members and 1 to 5 alkyl carbon atoms, heterocycloalkyl of 5 to 6 ring members and 1 to 5 alkyl carbon atoms, aminoalkyl of 2 to 5 carbon atoms, N-mono-substituted or N,N-disubstituted aminoalkyl of 2 to 5 alkyl carbon atoms wherein said substituents are radicals of alkyl of 1 to 3 carbon atoms, aralkyl of 1 to 3 alkyl carbon atoms radicals, carboxyalkyl of 1 to 5 carbon atoms, alkoxycarbonylalkyl of 1 to 5 alkyl carbon atoms, cyanoalkyl of 1 to 5 carbon atoms or hydroxyalkyl of 2 to 5 carbon atoms; more preferably, R20 represents hydrogen, alkyl of 1 to 5 carbon atoms, phenylalkyl of 1 to 3 alkyl carbon atoms, heterocycloalkyl of 5 to 6 ring members and 1 to 3 alkyl carbon atoms, or N-mono-substituted or N,N-disubstituted aminoalkyl of 2 to 3 carbon atoms wherein said substituents are alkyl radicals of 1 to 3 carbon atoms; and most preferably, R20 represents hydrogen, methyl, ethyl, propyl, isopropyl, isobutyl, benzyl, 2-(1-pyrrolidinyl)ethyl, 2-(1-piperidinyl)ethyl, 2-(1-piperazinyl)ethyl, 2-(4-methylpiperazin-1-yl)ethyl, 2-(1-morpholinyl)ethyl, 2-(1-thiamorpholinyl)ethyl or 2-(N,N-dimethylamino)ethyl radicals;
R21 represents hydrogen or alkyl radicals; preferably, R21 represents hydrogen radical or alkyl radical of 1 to 3 carbon atoms; more preferably, R21 represents hydrogen or methyl radicals; and most preferably, R21 represents a hydrogen radical; or
the radical of formula xe2x80x94NR20R21 represents a heterocyclo radical; preferably, the radical of formula xe2x80x94NR20R21 represents a 5 to 6 ring member heterocyclo radical; more preferably, the radical of formula xe2x80x94NR20R21 represents pyrrolidinyl, piperidinyl, piperazinyl, 4-methylpiperazinyl, 4-benzylpiperazinyl, morpholinyl or thiamorpholinyl radicals; and
R22 represents alkyl or R20R21N-alkyl radicals; preferably, R22 represents alkyl or R20R21N-alkyl radicals wherein alkyl is 1 to 3 carbon atoms; and more preferably, R22 represents alkyl radical of 1 to 3 carbon atoms; and
preferably R4 represents benzothiazol-5-yl, benzothiazol-6-yl, 2-amino-benzothiazol-5-yl, 2-(methoxycarbonylamino)benzothiazol-5-yl, 2-amino-benzothiazol-6-yl, 2-(methoxycarbonylamino)benzothiazol-6-yl, 5-benzoxazolyl, 6-benzoxazolyl, 6-benzopyranyl, 3,4-dihydrobenzopyran-6-yl, 7-benzopyranyl, 3,4-dihydrobenzopyran-7-yl, 2,3-dihydrobenzofuran-5-yl, benzofuran-5-yl, 1,3-benzodioxol-5-yl, 2-methyl-1,3-benzodioxol-5-yl, 2,2-dimethyl-1,3-benzodioxol-5-yl, 2,2-dideutero-1,3-benzodioxol-5-yl, 2,2-difluoro-1,3-benzodioxol-5-yl, 1,4-benzodioxan-6-yl, 5-benzimidazolyl, 2-(methoxycarbonylamino)benzimidazol-5-yl, 6-quinolinyl, 7-quinolinyl, 6-isoquinolinyl or 7-isoquinolinyl radicals; more preferably, R4 represents benzothiazol-5-yl, benzothiazol-6-yl, benzoxazol-5-yl, 2,3-dihydrobenzofuran-5-yl, benzofuran-5-yl, 1,3-benzodioxol-5-yl, 2-methyl-1,3-benzodioxol-5-yl, 2,2-dimethyl-1,3-benzodioxol-5-yl, 2,2-dideutero-1,3-benzodioxol-5-yl, 2,2-difluoro-1,3-benzodioxol-5-yl, 1,4-benzodioxan-6-yl, 2-(methoxycarbonylamino)benzothiazol-5-yl, 2-(methoxycarbonylamino)benzothiazol-6-yl or 2-(methoxycarbonylamino)benzimidazol-5-yl radicals; and most preferably, R4 represents benzothiazol-5-yl, benzothiazol-6-yl, 2,3-dihydrobenzofuran-5-yl, benzofuran-5-yl, 1,3-benzodioxol-5-yl, 2-methyl-1,3-benzodioxol-5-yl, 2,2-dimethyl-1,3-benzodioxol-5-yl, 2,2-dideutero-1,3-benzodioxol-5-yl, 2,2-difluoro-1,3-benzodioxol-5-yl, 1,4-benzodioxan-6-yl, 2-(methoxycarbonylamino)benzothiazol-6-yl or 2-(methoxycarbonylamino)benzimidazol-5-yl radicals; and
R5 represents an alkyl, alkenyl, alkynyl or aralkyl radicals; preferably, R5 represents an alkyl radical of 1-5 carbon atoms, alkenyl radical of 2-5 carbon atoms, alkynyl radical of 2-5 carbon atoms or aryl substituted alkyl of 1-5 carbon atoms; more preferably, R5 represents an alkyl radical of 1-5 carbon atoms, alkenyl radical of 3-4 carbon atoms, alkynyl radical of 3-4 carbon atoms or aryl substituted alkyl of 1-4 carbon atoms; even more preferably, R5 represents an alkyl radical of 1-5 carbon atoms or phenyl substituted alkyl of 2-4 carbon atoms; and most preferably, R5 represents an methyl, ethyl, propyl, isopropyl or 2-phenylethyl radicals.
Preferably, the absolute stereochemistry of the carbon atom of xe2x80x94CH(OH)xe2x80x94 group is (R) and the absolute stereochemistry of the carbon atoms of xe2x80x94CH(R1)xe2x80x94 and xe2x80x94CH(R2)xe2x80x94 groups is (S).
A family of compounds of particular interest within Formula I are compounds embraced by the formula 
or a pharmaceutically acceptable salt, prodrug or ester thereof, wherein t, R1, R2, R3, R4 and R5 are as defined above.
A family of compounds of further interest within Formula II are compounds embraced by the formula 
or a pharmaceutically acceptable salt, prodrug or ester thereof, wherein t, R1, R2, R3, R4 and R5 are as defined above.
A more preferred family of compounds within Formula III consists of compounds or a pharmaceutically acceptable salt, prodrug or ester thereof, wherein t represents 2;
R1 represents methyl or ethyl radicals;
R2 represents a benzyl, 4-fluorophenylmethyl or cyclohexylmethyl radical;
R3 represents propyl, isoamyl, isobutyl, butyl, cyclohexyl, cycloheptyl, cyclopentylmethyl or cyclohexylmethyl radicals;
R4 represents 2,3-dihydrobenzofuran-5-yl, 1,3-benzodioxol-5-yl, 2-methyl-1,3-benzodioxol-5-yl, 2,2-dimethyl-1,3-benzodioxol-5-yl, benzothiazol-6-yl, 2,2-dideutero-1,3-benzodioxol-5-yl, 2,2-difluoro-1,3-benzodioxol-5-yl or 1,4-benzodioxan-6-yl radicals; and
R5 represents methyl, ethyl, propyl, isopropyl or 2-phenylethyl radicals.
Compounds of interest include the following:
N-[2R-hydroxy-3-[(2-methylpropyl)[(1,3-benzodioxol-5-yl)sulfonyl]amino]-1S-(phenylmethyl)propyl]-2S-methyl-3-(methylsulfonyl)propanamide;
N-[2R-hydroxy-3-[(2-methylpropyl)[(1,4-benzodioxan-6-yl)sulfonyl]amino]-1S-(phenylmethyl)propyl]-2S-methyl-3-(methylsulfonyl)propanamide;
N-[2R-hydroxy-3-[(2-methylpropyl)[(benzothiazol-6-yl)sulfonyl]amino]-1S-(phenylmethyl)propyl]-2S-methyl-3-(methylsulfonyl)propanamide;
N-[2R-hydroxy-3-[(2-methylpropyl)[(benzothiazol-5-yl)sulfonyl]amino]-1S-(phenylmethyl)propyl]-2S-methyl-3-(methylsulfonyl)propanamide; and
N-[2R-hydroxy-3-[(2-methylpropyl)[(2,3-dihydrobenzofuran-5-yl)sulfonyl]amino]-1S-(phenylmethyl)propyl]-2S-methyl-3-(methylsulfonyl)propanamide.
As utilized herein, the term xe2x80x9calkylxe2x80x9d, alone or in combination, means a straight-chain or branched-chain alkyl radical containing preferably from 1 to 8 carbon atoms, more preferably from 1 to 5 carbon atoms, most preferably 1-3 carbon atoms. Examples of such radicals include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, iso-amyl, hexyl, octyl and the like. The term xe2x80x9chydroxyalkylxe2x80x9d, alone or in combination, means an alkyl radical as defined above wherein at least one hydrogen radical is replaced with a hydroxyl radical, preferably 1-3 hydrogen radicals are replaced by hydroxyl radicals, more preferably, 1-2 hydrogen radicals are replaced by hydroxyl radicals, and most preferably, one hydrogen radical is replaced by a hydroxyl radical. The term xe2x80x9calkenylxe2x80x9d, alone or in combination, means a straight-chain or branched-chain hydrocarbon radical having one or more double bonds and containing preferably from 2 to 8 carbon atoms, more preferably from 2 to 5 carbon atoms, most preferably from 2 to 3 carbon atoms. Examples of suitable alkenyl radicals include ethenyl, propenyl, 2-methylpropenyl, 1,4-butadienyl and the like. The term xe2x80x9calkynylxe2x80x9d, alone or in combination, means a straight-chain or branched chain hydrocarbon radical having one or more triple bonds and containing preferably from 2 to 8 carbon atoms, more preferably from 2 to 5 carbon atoms, most preferably from 2 to 3 carbon atoms. Examples of alkynyl radicals include ethynyl, propynyl (propargyl), butynyl and the like. The term xe2x80x9calkoxyxe2x80x9d, alone or in combination, means an alkyl ether radical wherein the term alkyl is as defined above. Examples of suitable alkyl ether radicals include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, iso-butoxy, sec-butoxy, tert-butoxy and the like. The term xe2x80x9ccycloalkylxe2x80x9d, alone or in combination, means a saturated or partially saturated monocyclic, bicyclic or tricyclic alkyl radical wherein each cyclic moiety contains preferably from 3 to 8 carbon atom ring members, more preferably from 3 to 7 carbon atom ring members, most preferably from 5 to 6 carbon atom ring members, and which may optionally be a benzo fused ring system which is optionally substituted as defined herein with respect to the definition of aryl. Examples of such cycloalkyl radicals include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, octahydronaphthyl, 2,3-dihydro-1H-indenyl, adamantyl and the like. xe2x80x9cBicyclicxe2x80x9d and xe2x80x9ctricyclicxe2x80x9d as used herein are intended to include both fused ring systems, such as naphthyl and xcex2-carbolinyl, and substituted ring systems, such as biphenyl, phenylpyridyl, naphthyl and diphenylpiperazinyl. The term xe2x80x9ccycloalkylalkylxe2x80x9d means an alkyl radical as defined above which is substituted by a cycloalkyl radical as defined above. Examples of such cycloalkylalkyl radicals include cyclopropylmethyl, cyclobutylmethyl. cyclopentylmethyl, cyclohexylmethyl, 1-cyclopentylethyl, 1-cyclohexylethyl, 2-cyclopentylethyl, 2-cyclohexylethyl, cyclobutylpropyl, cyclopentylpropyl, cyclohexylbutyl and the like. The term xe2x80x9cbenzoxe2x80x9d, alone or in combination, means the divalent radical C6H4xe2x95x90derived from benzene. The term xe2x80x9carylxe2x80x9d, alone or in combination, means a phenyl or naphthyl radical which is optionally substituted with one or more substituents selected from alkyl, alkoxy, halogen, hydroxy, amino, nitro, cyano, haloalkyl, carboxy, alkoxycarbonyl, cycloalkyl, heterocyclo, alkanoylamino, amido, amidino, alkoxycarbonylamino, N-alkylamidino, alkylamino, dialkylamino, N-alkylamido, N,N-dialkylamido, aralkoxycarbonylamino, alkylthio, alkylsulfinyl, alkylsulfonyl and the like. Examples of aryl radicals are phenyl, p-tolyl, 4-methoxyphenyl, 4-(tert-butoxy)phenyl, 3-methyl-4-methoxyphenyl, 4-CF3-phenyl, 4-fluorophenyl, 4-chlorophenyl, 3-nitrophenyl, 3-aminophenyl, 3-acetamidophenyl, 4-acetamidophenyl, 2-methyl-3-acetamidophenyl, 2-methyl-3-aminophenyl, 3-methyl-4-aminophenyl, 2-amino-3-methylphenyl, 2,4-dimethyl-3-aminophenyl, 4-hydroxyphenyl, 3-methyl-4-hydroxyphenyl, 1-naphthyl, 2-naphthyl, 3-amino-1-naphthyl, 2-methyl-3-amino-1-naphthyl, 6-amino-2-naphthyl, 4,6-dimethoxy-2-naphthyl, piperazinylphenyl and the like. The terms xe2x80x9caralkylxe2x80x9d and xe2x80x9caralkoxyxe2x80x9d, alone or in combination, means an alkyl or alkoxy radical as defined above in which at least one hydrogen atom is replaced by an aryl radical as defined above, such as benzyl, benzyloxy, 2-phenylethyl, dibenzylmethyl, hydroxyphenylmethyl, methylphenylmethyl, diphenylmethyl, diphenylmethoxy, 4-methoxyphenylmethoxy and the like. The term xe2x80x9caralkoxycarbonylxe2x80x9d, alone or in combination, means a radical of the formula aralkyl-Oxe2x80x94C(O)xe2x80x94 in which the term xe2x80x9caralkylxe2x80x9d has the significance given above. Examples of an aralkoxycarbonyl radical are benzyloxycarbonyl and 4-methoxyphenylmethoxycarbonyl. The term xe2x80x9caryloxyxe2x80x9d means a radical of the formula aryl-Oxe2x80x94 in which the term aryl has the significance given above. The term xe2x80x9calkanoylxe2x80x9d, alone or in combination, means an acyl radical derived from an alkanecarboxylic acid, examples of which include acetyl, propionyl, butyryl, valeryl, 4-methylvaleryl, and the like. The term xe2x80x9ccycloalkylcarbonylxe2x80x9d means an acyl radical of the formula cycloalkyl-C(O)xe2x80x94 in which the term xe2x80x9ccycloalkylxe2x80x9d has the significance give above, such as cyclopropylcarbonyl, cyclohexylcarbonyl, adamantylcarbonyl, 1,2,3,4-tetrahydro-2-naphthoyl, 2-acetamido-1,2,3,4-tetrahydro-2-naphthoyl, 1-hydroxy-1,2,3,4-tetrahydro-6-naphthoyl and the like. The term xe2x80x9caralkanoylxe2x80x9d means an acyl radical derived from an aryl-substituted alkanecarboxylic acid such as phenylacetyl, 3-phenylpropionyl(hydrocinnamoyl), 4-phenylbutyryl, (2-naphthyl)acetyl, 4-chlorohydrocinnamoyl, 4-aminohydrocinnamoyl, 4-methoxyhydrocinnamoyl, and the like. The term xe2x80x9caroylxe2x80x9d means an acyl radical derived from an arylcarboxylic acid, xe2x80x9carylxe2x80x9d having the meaning given above. Examples of such aroyl radicals include substituted and unsubstituted benzoyl or napthoyl such as benzoyl, 4-chlorobenzoyl, 4-carboxybenzoyl, 4-(benzyloxycarbonyl)benzoyl, 1-naphthoyl, 2-naphthoyl, 6-carboxy-2 naphthoyl, 6-(benzyloxycarbonyl)-2-naphthoyl, 3-benzyloxy-2-naphthoyl, 3-hydroxy-2-naphthoyl, 3-(benzyloxyformamido)-2-naphthoyl, and the like. The terms xe2x80x9cheterocyclo,xe2x80x9d alone or in combination, means a saturated or partially unsaturated monocyclic, bicyclic or tricyclic heterocycle radical containing at least one, preferably 1 to 4, more preferably 1 to 2, nitrogen, oxygen or sulfur atom ring member and having preferably 3 to 8 ring members in each ring, more preferably 3 to 7 ring members in each ring and most preferably 5 to 6 ring members in each ring. xe2x80x9cHeterocycloxe2x80x9d is intended to include sulfones, sulfoxides, N-oxides of tertiary nitrogen ring members, and carbocyclic fused and benzo fused ring systems. Such heterocyclo radicals may be optionally substituted on at least one, preferably 1 to 4, more preferably 1 to 2, carbon atoms by halogen, alkyl, alkoxy, hydroxy, oxo, aryl, aralkyl, heteroaryl. heteroaralkyl, amidino, N-alkylamidino, alkoxycarbonylamino, alkylsulfonylamino and the like, and/or on a secondary nitrogen atom (i.e., xe2x80x94NHxe2x80x94) by hydroxy, alkyl, aralkoxycarbonyl, alkanoyl, heteroaralkyl, phenyl or phenylalkyl and/or on a tertiary nitrogen atom (i.e., xe2x95x90Nxe2x80x94) by oxido. xe2x80x9cHeterocycloalkylxe2x80x9d means an alkyl radical as defined above in which at least one hydrogen atom is replaced by a heterocyclo radical as defined above, such as pyrrolidinylmethyl, tetrahydrothienylmethyl, pyridylmethyl and the like. The term xe2x80x9cheteroarylxe2x80x9d, alone or in combination, means an aromatic heterocyclo radical as defined above, which is optionally substituted as defined above with respect to the definitions of aryl and heterocyclo. Examples of such heterocyclo and heteroaryl groups are pyrrolidinyl, piperidinyl, piperazinyl, morpholinyl, thiamorpholinyl, pyrrolyl, imidazolyl (e.g., imidazol 4-yl, 1-benzyloxycarbonylimidazol-4-yl, etc.), pyrazolyl, pyridyl, (e.g., 2-(1-piperidinyl)pyridyl and 2-(4-benzylpiperazin-1-yl-1-pyridinyl, etc.), pyrazinyl, pyrimidinyl, furyl, tetrahydrofuryl, thienyl, tetrahydrothienyl and its sulfoxide and sulfone derivatives, triazolyl, oxazolyl, thiazolyl, indolyl (e.g., 2-indolyl, etc.), quinolinyl, (e.g., 2-quinolinyl, 3-quinolinyl, 1-oxido-2-quinolinyl, etc.), isoquinolinyl (e.g., 1-isoquinolinyl, 3-isoquinolinyl, etc.), tetrahydroquinolinyl (e.g., 1,2,3,4-tetrahydro-2-quinolyl, etc.), 1,2,3,4-tetrahydroisoquinolinyl (e.g., 1,2,3,4-tetrahydro-1-oxo-isoquinolinyl, etc.), quinoxalinyl, xcex2-carbolinyl, 2-benzofurancarbonyl, 1-,2-,4- or 5-benzimidazolyl, methylenedioxyphen-4-yl, methylenedioxyphen-5-yl, ethylenedioxyphenyl, benzothiazolyl, benzopyranyl, benzofuryl, 2,3-dihydrobenzofuryl, benzoxazolyl, thiophenyl and the like. The term xe2x80x9cheteroaralkylxe2x80x9d, alone or in combination, means an alkyl radical as defined above in which at least one hydrogen atom is replaced by an heteroaryl radical as defined above, such as benzofurylmethyl, 3-furylpropyl, quinolinylmethyl, 2-thienylethyl, pyridylmethyl, 2-pyrrolylpropyl, 1-imidazolylethyl and the like. The term xe2x80x9ccycloalkylalkoxycarbonylxe2x80x9d means an acyl group derived from a cycloalkylalkoxycarboxylic acid of the formula cycloalkylalkyl-Oxe2x80x94COOH wherein cycloalkylalkyl has the meaning given above. The term xe2x80x9caryloxyalkanoylxe2x80x9d means an acyl radical of the formula aryl-O-alkanoyl wherein aryl and alkanoyl have the meaning given above. The term xe2x80x9cheterocycloalkoxycarbonylxe2x80x9d means an acyl group derived from heterocycloalkyl-Oxe2x80x94COOH wherein heterocycloalkyl is as defined above. The term xe2x80x9cheterocycloalkanoylxe2x80x9d is an acyl radical derived from a heterocycloalkylcarboxylic acid wherein heterocyclo has the meaning given above. The term xe2x80x9cheterocycloalkoxycarbonylxe2x80x9d means an acyl radical derived from a heterocycloalkyl-Oxe2x80x94COOH wherein heterocyclo has the meaning given above. The term xe2x80x9cheteroaryloxycarbonylxe2x80x9d means an acyl radical derived from a carboxylic acid represented by heteroaryl-Oxe2x80x94COOH wherein heteroaryl has the meaning given above. The term xe2x80x9caminocarbonylxe2x80x9d alone or in combination, means an amino-substituted carbonyl (carbamoyl) group wherein the amino group can be a primary, secondary or tertiary amino group containing substituents selected from alkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl radicals and the like. The term xe2x80x9caminoalkanoylxe2x80x9d means acyl group derived from an amino-substituted alkylcarboxylic acid wherein the amino group can be a primary, secondary or tertiary amino group containing substituents selected from alkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl radicals and the like. The term xe2x80x9chalogenxe2x80x9d means fluorine, chlorine, bromine or iodine. The term xe2x80x9chaloalkylxe2x80x9d means an alkyl radical having the meaning as defined above wherein one or more hydrogens are replaced with a halogen. Examples of such haloalkyl radicals include chloromethyl, 1-bromoethyl, fluoromethyl, difluoromethyl, trifluoromethyl, 1,1,1-trifluoroethyl and the like. The term xe2x80x9cleaving groupxe2x80x9d (L or W) generally refers to groups readily displaceable by a nucleophile, such as an amine, a thiol or an alcohol nucleophile. Such leaving groups are well known in the art. Examples of such leaving groups include, but are not limited to, N-hydroxysuccinimide, N-hydroxybenzotriazole, halides, triflates, tosylates and the like. Preferred leaving groups are indicated herein where appropriate.
Procedures for preparing the compounds of Formula I are set forth below. It should be noted that the general procedure is shown as it relates to preparation of compounds having the specified stereochemistry, for example, wherein the absolute stereochemistry about the hydroxyl group is designated as (R). However, such procedures are generally applicable to those compounds of opposite configuration, e.g., where the stereochemistry about the hydroxyl group is (S). In addition, the compounds having the (R) stereochemistry can be utilized to produce those having the (S) stereochemistry. For example, a compound having the (R) stereochemistry can be inverted to the (S) stereochemistry using well-known methods.
The compounds of the present invention represented by Formula I above can be prepared utilizing the following general procedures as schematically shown in Schemes I and II. 
An N-protected chloroketone derivative of an amino acid having the formula: 
wherein P represents an amino protecting group, and R2 is as defined above, is reduced to the corresponding alcohol utilizing an appropriate reducing agent. Suitable amino protecting groups are well known in the art and include carbobenzoxy, t-butoxycarbonyl, and the like. A preferred amino protecting group is carbobenzoxy. A preferred N-protected chloroketone is N-benzyloxycarbonyl-L-phenylalanine chloromethyl ketone. A preferred reducing agent is sodium borohydride. The reduction reaction is conducted at a temperature of from xe2x88x9210xc2x0 C. to about 25xc2x0 C., preferably at about 0xc2x0 C., in a suitable solvent system such as. for example, tetrahydrofuran, and the like. The N-protected chloroketones are commercially available, e.g., such as from Bachem, Inc., Torrance, Calif. Alternatively, the chloroketones can be prepared by the procedure set forth in S. J. Fittkau, J. Prakt. Chem., 3, 1037 (1973), and subsequently N-protected utilizing procedures which are well known in the art.
The halo alcohol can be utilized directly, as described below, or, preferably, is reacted, preferably at room temperature, with a suitable base in a suitable solvent system to produce an N-protected amino epoxide of the formula: 
wherein P and R2 are as defined above. Suitable solvent systems for preparing the amino epoxide include ethanol, methanol, isopropanol, tetrahydrofuran, dioxane, and the like including mixtures thereof. Suitable bases for producing the epoxide from the reduced chloroketone include potassium hydroxide, sodium hydroxide, potassium t-butoxide, DBU and the like. A preferred base is potassium hydroxide.
Alternatively, a protected amino epoxide can be prepared, such as in co-owned and co-pending PCT Patent Application Serial No. PCT/US93/04804 (WO 93/23388) and PCT/US94/12201, and US Patent Application Ser. No. 08/376,340 now U.S. Pat. No. 5,831,117, each of which is incorporated herein by reference in their entirety) disclose methods of preparing chiral epoxide, chiral cyanohydrin, chiral amine and other chiral intermediates useful in the preparation of retroviral protease inhibitors, starting with a DL-, D- or L-amino acid which is reacted with a suitable amino-protecting group in a suitable solvent to produce an amino-protected amino acid ester. For the purposes of illustration, a protected L-amino acid with the following formula will be used to prepare the inhibitors of this invention: 
wherein P3 represents carboxyl-protecting group, e.g., methyl, ethyl, benzyl, tertiary-butyl, 4-methoxyphenylmethyl and the like; R2 is as defined above; and p1 and p2 and Pxe2x80x2 independently are selected from amine protecting groups, including but not limited to, aralkyl, substituted aralkyl, cycloalkenylalkyl and substituted cycloalkenylalkyl, allyl, substituted allyl, acyl, alkoxycarbonyl, aralkoxycarbonyl and silyl. Examples of aralkyl include, but are not limited to benzyl, ortho-methylbenzyl, trityl and benzhydryl, which can be optionally substituted with halogen, alkyl of C1-C8, alkoxy, hydroxy, nitro, alkylene, amino, alkylamino, acylamino and acyl, or their salts, such as phosphonium and ammonium salts. Examples of aryl groups include phenyl, naphthalenyl, indanyl, anthracenyl, durenyl, 9-(9-phenylfluorenyl) and phenanthrenyl, cycloalkenylalkyl or substituted cycloalkylenylalkyl radicals containing cycloalkyls of C6-C10. Suitable acyl groups include carbobenzoxy, t-butoxycarbonyl, isobutoxycarbonyl, benzoyl, substituted benzoyl, butyryl, acetyl, tri-fluoroacetyl, tri-chloroacetyl, phthaloyl and the like. Preferably p1 and p2 are independently selected from aralkyl and substituted aralkyl. More preferably, each of p1 and p2 is benzyl.
Additionally, the P1 and/or p2 and/or Pxe2x80x2 protecting groups can form a heterocyclic ring with the nitrogen to which they are attached, for example, 1,2-bis(methylene)benzene, phthalimidyl, succinimidyl, maleimidyl and the like and where these heterocyclic groups can further include adjoining aryl and cycloalkyl rings. In addition, the heterocyclic groups can be mono-, di- or tri-substituted, e.g., nitrophthalimidyl. The term silyl refers to a silicon atom optionally substituted by one or more alkyl, aryl and aralkyl groups.
Suitable silyl protecting groups include, but are not limited to, trimethylsilyl, triethylsilyl, tri-isopropylsilyl, tert-butyldimethylsilyl, dimethylphenylsilyl, 1,2-bis(dimethylsilyl)benzene, 1,2-bis(dimethylsilyl)ethane and diphenylmethylsilyl. Silylation of the amine functions to provide mono- or bis-disilylamine can provide derivatives of the aminoalcohol, amino acid, amino acid esters and amino acid amide. In the case of amino acids, amino acid esters and amino acid amides, reduction of the carbonyl function provides the required mono- or bis-silyl aminoalcohol. Silylation of the aminoalcohol can lead to the N,N,O-tri-silyl derivative. Removal of the silyl function from the silyl ether function is readily accomplished by treatment with, for example, a metal hydroxide or ammonium flouride reagent, either as a discrete reaction step or in situ during the preparation of the amino aldehyde reagent. Suitable silylating agents are, for example, trimethylsilyl chloride, tert-buty-dimethylsilyl chloride, phenyldimethylsilyl chlorie, diphenylmethylsilyl chloride or their combination products with imidazole or DMF. Methods for silylation of amines and removal of silyl protecting groups are well known to those skilled in the art. Methods of preparation of these amine derivatives from corresponding amino acids, amino acid amides or amino acid esters are also well known to those skilled in the art of organic chemistry including amino acid/amino acid ester or aminoalcohol chemistry.
The amino-protected L-amino acid ester is then reduced, to the corresponding alcohol. For example, the amino-protected L-amino acid ester can be reduced with diisobutylaluminum hydride at xe2x88x9278xc2x0 C. in a suitable solvent such as toluene. Preferred reducing agents include lithium aluminium hydride, lithium borohydride, sodium borohydride, borane, lithium tri-ter-butoxyaluminum hydride, borane/THF complex. Most preferably, the reducing agent is diisobutylaluminum hydride (DiBAL-H) in toluene. The resulting alcohol is then converted, for example, by way of a Swern oxidation, to the corresponding aldehyde of the formula: 
wherein p1, p2 and R2 are as defined above. Thus, a dichloromethane solution of the alcohol is added to a cooled (xe2x88x9275 to xe2x88x9268xc2x0 C.) solution of oxalyl chloride in dichloromethane and DMSO in dichloromethane and stirred for 35 minutes.
Acceptable oxidizing reagents include, for example, sulfur trioxide-pyridine complex and DMSO, oxalyl chloride and DMSO, acetyl chloride or anhydride and DMSO, trifluoroacetyl chloride or anhydride and DMSO, methanesulfonyl chloride and DMSO or tetrahydro thiaphene-S-oxide, toluenesulfonyl bromide and DMSO, trifluoromethanesulfonyl anhydride (triflic anhydride) and DMSO, phosphorus pentachloride and DMSO, dimethylphosphoryl chloride and DMSO and isobutyl chloroformate and DMSO. The oxidation conditions reported by Reetz et al [Angew Chem., 99, p. 1186, (1987)], Angew Chem. int. Ed. Engl., 26, p. 1141, 1987) employed oxalyl chloride and DMSO at xe2x88x9278xc2x0 C.
The preferred oxidation method described in this invention is sulfur trioxide pyridine complex, triethylamine and DMSO at room temperature. This system provides excellent yields of the desired chiral protected amino aldehyde usable without the need for purification i.e., the need to purify kilograms of intermediates by chromatography is eliminated and large scale operations are made less hazardous. Reaction at room temperature also eliminated the need for the use of low temperature reactor which makes the process more suitable for commercial production.
The reaction may be carried out under an inert atmosphere such as nitrogen or argon, or normal or dry air, under atmospheric pressure or in a sealed reaction vessel under positive pressure. Preferred is a nitrogen atmosphere. Alternative amine bases include, for example, tri-butyl amine, tri-isopropyl amine, N-methylpiperidine, N-methyl morpholine, azabicyclononane, diisopropylethylamine, 2,2,6,6-tetramethylpiperidine, N,N-dimethylaminopyridine, or mixtures of these bases. Triethylamine is a preferred base. Alternatives to pure DMSO as solvent include mixtures of DMSO with non-protic or halogenated solvents such as tetrahydrofuran, ethyl acetate, toluene, xylene, dichloromethane, ethylene dichloride and the like. Dipolar aprotic co-solvents include acetonitrile, dimethylformamide, dimethylacetamide, acetamide, tetramethyl urea and its cyclic analog, N-methylpyrrolidone, sulfolane and the like. Rather than N,N-dibenzylphenylalaninol as the aldehyde precursor, the phenylalaninol derivatives discussed above can be used to provide the corresponding N-monosubstituted [either p1 or P2xe2x95x90H] or N,N-disubstituted aldehyde.
In addition, hydride reduction of an amide or ester derivative of the corresponding benzyl (or other suitable protecting group) nitrogen protected phenylalanine, substituted phenylalanine or cycloalkyl analog of phenylalanine derivative can be carried out to provide the aldehydes. Hydride transfer is an additional method of aldehyde synthesis under conditions where aldehyde condensations are avoided, cf, Oppenauer Oxidation.
The aldehydes of this process can also be prepared by methods of reducing protected phenylalanine and phenylalanine analogs or their amide or ester derivatives by, e.g., sodium amalgam with HCl in ethanol or lithium or sodium or potassium or calcium in ammonia. The reaction temperature may be from about xe2x88x9220xc2x0 C. to about 45xc2x0 C., and preferably from abut 5xc2x0 C. to about 25xc2x0 C. Two additional methods of obtaining the nitrogen protected aldehyde include oxidation of the corresponding alcohol with bleach in the presence of a catalytic amount of 2,2,6,6-tetramethyl-1-pyridyloxy free radical. In a second method, oxidation of the alcohol to the aldehyde is accomplished by a catalytic amount of tetrapropylammonium perruthenate in the presence of N-methylmorpholine-N-oxide.
Alternatively, an acid chloride derivative of a protected phenylalanine or phenylalanine derivative as disclosed above can be reduced with hydrogen and a catalyst such as Pd on barium carbonate or barium sulphate, with or without an additional catalyst moderating agent such as sulfur or a thiol (Rosenmund Reduction).
The aldehyde resulting from the Swern oxidation is then reacted with a halomethyllithium reagent, which reagent is generated in situ by reacting an alkyllithium or arylithium compound with a dihalomethane represented by the formula X1CH2X2 wherein X1 and X2 independently represent I, Br or Cl. For example, a solution of the aldehyde and chloroiodomethane in THF is cooled to xe2x88x9278xc2x0 C. and a solution of n-butyllithium in hexane is added. The resulting product is a mixture of diastereomers of the corresponding amino-protected epoxides of the formulas: 
The diastereomers can be separated e.g., by chromatography, or, alternatively, once reacted in subsequent steps the diastereomeric products can be separated. A D-amino acid can be utilized in place of the L-amino acid in order to prepare compounds having an (S) stereochemistry at the carbon bonded to R2.
The addition of chloromethylithium or bromomethylithium to a chiral amino aldehyde is highly diastereoselective. Preferably, the chloromethyllithium or bromomethylithium is generated in-situ from the reaction of the dihalomethane and n-butyllithium. Acceptable methyleneating halomethanes include chloroiodomethane, bromochloromethane, dibromomethane, diiodomethane, bromofluoromethane and the like. The sulfonate ester of the addition product of, for example, hydrogen bromide to formaldehyde is also a methyleneating agent. Tetrahydrofuran is the preferred solvent, however alternative solvents such as toluene, dimethoxyethane, ethylene dichloride, methylene chloride can be used as pure solvents or as a mixture. Dipolar aprotic solvents such as acetonitrile, DMF, N-methylpyrrolidone are useful as solvents or as part of a solvent mixture. The reaction can be carried out under an inert atmosphere such as nitrogen or argon. For n-butyl lithium can be substituted other organometalic reagents reagents such as methyllithium, tert-butyl lithium, sec-butyl lithium, phenyllithium, phenyl sodium and the like. The reaction can be carried out at temperatures of between about xe2x88x9280xc2x0 C. to 0xc2x0 C. but preferably between about xe2x88x9280xc2x0 C. to xe2x88x9220xc2x0 C. The most preferred reaction temperatures are between xe2x88x9240xc2x0 C. to xe2x88x9215xc2x0 C. Reagents can be added singly but multiple additions are preferred in certain conditions. The preferred pressure of the reaction is atmospheric however a positive pressure is valuable under certain conditions such as a high humidity environment.
Alternative methods of conversion to the epoxides of this invention include substitution of other charged methylenation precurser species followed by their treatment with base to form the analogous anion. Examples of these species include trimethylsulfoxonium tosylate or triflate, tetramethylammonium halide, methyldiphenylsulfoxonium halide wherein halide is chloride, bromide or iodide.
The conversion of the aldehydes of this invention into their epoxide derivative can also be carried out in multiple steps. For example, the addition of the anion of thioanisole prepared from, for example, a butyl or aryl lithium reagent, to the protected aminoaldehyde, oxidation of the resulting protected aminosulfide alcohol with well known oxidizing agents such as hydrogen peroxide, tert-butyl hypochlorite, bleach or sodium periodate to give a sulfoxide. Alkylation of the sulfoxide with, for example, methyl iodide or bromide, methyl tosylate, methyl mesylate, methyl triflate, ethyl bromide, isopropyl bromide, benzyl chloride or the like, in the presence of an organic or inorganic base Alternatively, the protected aminosulfide alcohol can be alkylated with, for example, the alkylating agents above, to provide a sulfonium salts that are subsequently converted into the subject epoxides with tert-amine or mineral bases.
The desired epoxides formed, using most preferred conditions, diastereoselectively in ratio amounts of at least about an 85:15 ratio (S:R). The product can be purified by chromatography to give the diastereomerically and enantiomerically pure product but it is more conveniently used directly without purification to prepare retroviral protease inhibitors. The foregoing process is applicable to mixtures of optical isomers as well as resolved compounds. If a particular optical isomer is desired, it can be selected by the choice of starting material, e.g., L-phenylalanine, D-phenylalanine, L-phenylalaninol, D-phenylalaninol, D-hexahydrophenylalaninol and the like, or resolution can occur at intermediate or final steps. Chiral auxiliaries such as one or two equivilants of camphor sulfonic acid, citric acid, camphoric acid, 2-methoxyphenylacetic acid and the like can be used to form salts, esters or amides of the compounds of this invention. These compounds or derivatives can be crystallized or separated chromatographically using either a chiral or achiral column as is well known to those skilled in the art.
The amino epoxide is then reacted, in a suitable solvent system, with an equal amount, or preferably an excess of, a desired amine of the formula R3NH2, wherein R3 is hydrogen or is as defined above. The reaction can be conducted over a wide range of temperatures, e.g., from about 10xc2x0 C. to about 100xc2x0 C., but is preferably, but not necessarily, conducted at a temperature at which the solvent begins to reflux. Suitable solvent systems include protic, non-protic and dipolar aprotic organic solvents such as, for example, those wherein the solvent is an alcohol, such as methanol, ethanol, isopropanol, and the like, ethers such as tetrahydrofuran, dioxane and the like, and toluene, N,N-dimethylformamide, dimethyl sulfoxide, and mixtures thereof. A preferred solvent is isopropanol. The resulting product is a 3-(N-protected amino)-3-(R2)-1-(NHR3)-propan-2-ol derivative (hereinafter referred to as an amino alcohol) can be represented by the formulas: 
wherein P, P1, P2, R2 and R3 are as described above. Alternatively, a haloalcohol can be utilized in place of the amino epoxide.
The amino alcohol defined above is then reacted in a suitable solvent with the sulfonyl chloride R4SO2Cl, the sulfonyl bromide R4SO2Br or the corresponding sulfonyl anhydride, preferably in the presence of an acid scavenger. Suitable solvents in which the reaction can be conducted include methylene chloride, tetrahydrofuran and the like. Suitable acid scavengers include triethylamine, pyridine and the like. The resulting sulfonamide derivative can be represented, depending on the epoxide utilized by the formulas 
wherein P, P1, P2, R2, R3 and R4 are as defined above. These intermediates are useful for preparing inhibitor compounds of the present invention.
Alternatively, the protected amino alcohol from the epoxide opening can be further protected at the newly introduced amino group with a protecting group Pxe2x80x2 which is not removed with the removal of the amino protecting groups P or P1 and P2, i.e., Pxe2x80x2 is selectively removable. One skilled in the art can choose appropriate combinations of Pxe2x80x2, P, P1 and P2. For example, suitable combinations are P=Cbz and Pxe2x80x2=Boc; Pxe2x80x2=Cbz and P=Boc; p1=Cbz, p2=benzyl and Pxe2x80x2=Boc; and P1=p2=benzyl and Pxe2x80x2=Boc. The resulting compound represented by the formula 
can be carried through the remainder of the synthesis to provide a compound of the formula 
wherein n, t, Pxe2x80x2, R1, R2, R3 and R5 are as defined above. The remainder of the synthesis above can be carried out as desired either by the addition of desired residues or groups one at a time or in a preformed molecule made up of more that one residue or group in one step. The former approach is the sequential synthesis method and the latter is the convergent synthesis method. Synthetic transformations are possible at this stage also. The protecting group Pxe2x80x2 is then selectively removed and the resulting amine is reacted with the sulfonyl chloride R4SO2Cl, the sulfonyl bromide R4SO2Br or the corresponding sulfonyl anhydride, preferably in the presence of an acid scavenger, to form the compounds of the present invention 
wherein n, t, R1, R2, R3, R4 and R5 are as defined above. This selective deprotection and conversion to the sulfonamide can be accomplished at either the end of the synthesis or at any appropriate intermediate step as desired. An example is outlined in Scheme II.
The sulfonyl halides of the formula R4SO2X can be prepared by the reaction of a suitable aryl, heteroaryl and benzo fused heterocyclo Grignard or lithium reagents with sulfuryl chloride, or sulfur dioxide followed by oxidation with a halogen, preferably chlorine. Aryl, heteroaryl and benzo fused heterocyclo Grignard or lithium reagents can be prepared from their corresponding halide (such as chloro or bromo) compounds which are commercially available or readily prepared from commercially available starting materials using known methods in the art. Also, thiols may be oxidized to sulfonyl chlorides using chlorine in the presence of water under carefully controlled conditions. Additionally, sulfonic acids, such as arylsulfonic acids, may be converted to sulfonyl halides using reagents such as PCl5, SOCl2, ClC(O)C(O)Cl and the like, and also to anhydrides using suitable dehydrating reagents. The sulfonic acids may in turn be prepared using procedures well known in the art. Some sulfonic acids are commercially available. In place of the sulfonyl halides, sulfinyl halides (R4SOX) or sulfenyl halides (R4SX) can be utilized to prepare compounds wherein the xe2x80x94SO2xe2x80x94 moiety is replaced by an xe2x80x94Sxe2x80x94 or xe2x80x94Sxe2x80x94 moiety, respectively. Arylsulfonic acids, benzo fused heterocyclo sulfonic acids or heteroaryl sulfonic acids can be prepared by sulfonation of the aromatic ring by well known methods in the art, such as by reaction with sulfuric acid, SO3, SO3 complexes, such as DMF(SO3), pyridine(SO3), N,N-dimethylacetamide(SO3), and the like. Preferably, arylsulfonyl halides are prepared from aromatic compounds by reaction with DMF(SO3) and SOCl2 or ClC(O)C(O)Cl. The reactions may be performed stepwise or in a single pot.
Arylsulfonic acids, benzo fused heterocyclo sulfonic acids, heteroaryl sulfonic acids, arylmercaptans, benzo fused heterocyclo mercaptans, heteroarylmercaptans, arylhalides, benzo fused heterocyclo halides, heteroarylhalides, and the like are commercially available or can be readily prepared from starting materials commercially available using standard methods well known in the art. For example, a number of sulfonic acids (R4SO3H) represented by the formulas 
wherein A, B, Z, R6, R7 and R9 are as defined above, have been prepared from 1,2-benzenedithiol, 2-mercaptanphenol, 1,2-benzenediol, 2-aminobenzothiazole, benzothiazole, 2-aminobenzimidazole, benzimidazole, and the like, which are commercially available, by Carter, U.S. Pat. No. 4,595,407; Ehrenfreund et al., U.S. Pat. No. 4,634,465; Yoder et al., J. Heterocycl. Chem. 4:166-167 (1967); Cole et al., Aust. J. Chem. 33:675-680 (1980); Cabiddu et al., Synthesis 797-798 (1976); Ncube et al., Tet. Letters 2345-2348 (1978); Ncube et al., Tet. Letters 255-256 (1977); Ansink and Cerfontain, Rec. Trav. Chim.Pays-Bas 108:395-403 (1989); and Kajihara and Tsuchiya, EP 638564 Al, each of which are incorporated herein. by reference in their entirety. For example, 1,2-benzenedithiol, 2-mercaptanphenol or 1,2-benzenediol can be reacted with R6R7C(Lxe2x80x2)2, where Lxe2x80x2 is as defined below, preferably, Br or I, in the presence of a base, such as hydroxide, or R6R7Cxe2x95x90O in the presence of acid, such as toluenesulfonic acid, or P2O5., to prepare the substituted benzo fused heterocycle of formula 
which can then be sulfonylated to the sulfonic acid above. For example, CF2Br2 or CD2Br2 can be reacted with 1,2-benzenedithiol, 2-mercaptanphenol or 1,2-benzenediol in the presence of base to produce the compounds 
respectively, wherein A and B are O or S and D is a deuterium atom. Also, when A and/or B represent S, the sulfur can be oxidized using the methods described below to the sulfone or sulfoxide derivatives.
Following preparation of the sulfonamide derivative, the amino protecting group P or P1 and P2 amino protecting groups are removed under conditions which will not affect the remaining portion of the molecule. These methods are well known in the art and include acid hydrolysis, hydrogenolysis and the like. A preferred method involves removal of the protecting group, e.g., removal of a carbobenzoxy group, by hydrogenolysis utilizing palladium on carbon in a suitable solvent system such as an alcohol, acetic acid, and the like or mixtures thereof. Where the protecting group is a t-butoxycarbonyl group, it can be removed utilizing an inorganic or organic acid. e.g., HCl or trifluoroacetic acid, in a suitable solvent system, e.g., dioxane or methylene chloride. The resulting product is the amine salt derivative.
Following neutralization of the salt, the amine is then coupled to the sulfone/sulfoxidealkanoyl compound or an optical isomer thereof (such as where the group xe2x80x94CH(R1)xe2x80x94 is R or S), corresponding to the formula 
wherein n, t and R5 are as defined above, and L is leaving group such as halide, anhydride, active ester, and the like. Alternatively, the sulfone/sulfoxide alkanoyl compound or an optical isomer thereof can be coupled to the protected amine 
followed by deprotection and coupling to R4SO2X, where X is Cl or Br and Pxe2x80x2, R2, R3 and R4 is as defined above.
Such sulfone/sulfoxidealkanoyl compounds where n is 1 can be prepared by reacting a mercaptan of the formula R5SH with a substituted methacrylate of the formula 
by way of a Michael Addition. Such substituted methacrylates are commercially available or readily prepared from commercially available starting materials using standard methods well known in the art. The Michael Addition is conducted in a suitable solvent and in the presence of a suitable base, to produce the corresponding thiol derivative represented by the formula 
wherein P3, R1 and R5 are as defined above. Suitable solvents in which he Michael Addition can be conducted include alcohols such as, for example, methanol, ethanol, butanol and the like, as well as ethers, e.g., THF, and, acetonitrile, DMF, DMSO, and the like, including mixtures thereof. Suitable bases include Group I metal alkoxides such as, for example sodium methoxide, sodium ethoxide, sodium butoxide and the like as well as Group I metal hydrides, such as sodium hydride, including mixtures thereof. The thiol derivative is converted into the corresponding sulfone or sulfoxide of the formula 
by oxidizing the thiol derivative with a suitable oxidation agent in a suitable solvent. Suitable oxidation agents include, for example, hydrogen peroxide, sodium meta-perborate, oxone (potassium peroxy monosulfate), meta-chloroperoxybenzoic acid, periodic acid and the like, including mixtures thereof. Suitable solvents include acetic acid (for sodium meta-perborate) and, for other peracids, ethers such as THF and dioxane, and acetonitrile, DMF and the like, including mixtures thereof.
The sulfone/sulfoxide is then converted into the corresponding free acid of the formula 
utilizing a suitable base, e.g., lithium hydroxide, sodium hydroxide, and the like, including mixtures thereof, in a suitable solvent, such as, for example, THF, acetonitrile, DMF, DMSO, methylene chloride and the like, including mixtures thereof. The free acid can then be converted into the sulfone/sulfoxidealkanoyl compound 
wherein n, t and R5 are as defined above, and L is leaving group such as halide, anhydride, active ester, and the like. Alternatively, the free acid can be resolved into its optical isomers (such as where the group xe2x80x94CH(R1)xe2x80x94 is R or S) using well known methods in the art, such as by forming diastereomeric salts or esters and crystallizing or chromatographing, and then converted into the sulfone/sulfoxidealkanoyl compound.
Alternatively, the thioether or corresponding protected thiol of formulas 
respectively, where n, L, R1 and R5 are as defined above, can be coupled to one of the amines 
followed by conversion to the protease inhibitors of the present invention. P4 is a sulfur protecting group, such as acetyl, benzoyl and the like. The acetyl and benzoyl groups can be removed by treatment with an inorganic base or an amine, preferably ammonia, in an appropriate solvent such as methanol, ethanol, isopropanol, toluene or tetrahydrofuran. The preferred solvent is methanol.
For example, one can couple the commercially available acid 
to one of the amines 
deacetylate the sulfur group, such as by hydrolysis with a suitable base, such as hydroxide, or an amine, such as ammonia, and then react the resulting thiol with R5Lxe2x80x2 agent, wherein R5 and Lxe2x80x2 are as defined above, to afford compounds with one of the following structures 
or specific diastereomeric isomers thereof. The sulfur can then be oxidized to the corresponding sulfone or sulfoxide using suitable oxidizing agents, as described above, to afford the desired intermediate followed by further reactions to prepare the sulfonamide inhibitor, or directly to the sulfonamide inhibitor. Alternatively, the acid or the P3 protected acid can be deacetylated, reacted with R5Lxe2x80x2 agent, deprotected and oxidized to the corresponding sulfone or sulfoxide using suitable oxidizing agents, as described above to afford the compound of formula 
wherein t and R5 are as defined above. This sulfone/sulfoxide carboxylic acid can then be coupled to the amine intermediate described above followed by further reaction to prepare the sulfonamide inhibitor, or to the sulfonamide amine compound to produce the sulfonamide inhibitor directly. The Lxe2x80x2 group of the R5Lxe2x80x2 agent is a leaving group. such as a halide (chloride, bromide, iodide), mesylate, tosylate or triflate. The reaction of the mercaptan with R5Lxe2x80x2 is performed in the presence of a suitable base, such as triethylamine, diisopropylethylamine, 1,8-diazabicyclo[5.4.0] undec-7-ene (DBu) and the like, in a suitable solvent such as toluene, tetrahydrofuran, or methylene chloride. The preferred base is DBU and the preferred solvent is toluene. Where R5 is a methyl group, R5Lxe2x80x2 can be methyl chloride, methyl bromide, methyl iodide, or dimethyl sulfate, and preferably methyl iodide.
Alternatively, a substituted methacrylate of the formula 
wherein Lxe2x80x2 represents a leaving group as previously defined, P3 is as defined above and R10 represents radicals which upon reduction of the double bond produce radicals of R1, is reacted with R5SM followed by oxidation, as described above, or a suitable sulfonating agent, such as, for example, a sulfinic acid represented by the formula R5SO2M wherein R5 is as defined above and M represents a metal adapted to form a salt of the acid, e.g., sodium, to produce the corresponding sulfone represented by the formula 
wherein P3, R5 and R10 are as defined above. The sulfone is then deprotected to form the corresponding carboxylic acid. For example, when P3 is a tertiary-butyl group, it can be removed by treatment with an acid, such as hydrochloric acid or trifluoracetic acid. The preferred method is using 4N hydrochloric acid in dioxane.
The resulting carboxylic acid is then asymmetrically hydrogenated utilizing an asymmetric hydrogenation catalyst such as, for example, a ruthenium-BINAP complex, to produce the reduced product, substantially enriched in the more desired isomer, represented by one of the formulas 
wherein R1 and R5 are as defined above. Where the more active isomer has the R-stereochemistry, a Ru(R-BINAP) asymmetric hydrogenation catalyst can be utilized. Conversely, where the more active isomer has the S-sterochemistry, a Ru(S-BINAP) catalyst can be utilized. Where both isomers are active, or where it is desired to have a mixture of the two diastereomers, a hydrogenation catalyst such as platinum or palladium on carbon can be utilized to reduce the above compound. The reduced compound is then coupled to an amine as described above.
The chemical reactions described above are generally disclosed in terms of their broadest application to the preparation of the compounds of this invention. Occasionally, the reactions may not be applicable as described to each compound included within the disclosed scope. The compounds for which this occurs will be readily recognized by those skilled in the art. In all such cases, either the reactions can be successfully performed by conventional modifications known to those skilled in the art, e.g., by appropriate protection of interfering groups, by changing to alternative conventional reagents, by routine modification of reaction conditions, and the like, or other reactions disclosed herein or otherwise conventional, will be applicable to the preparation of the corresponding compounds of this invention. In all preparative methods, all starting materials are known or readily prepared from known starting materials.
Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The following preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.
All reagents were used as received without purification. All proton and carbon NMR spectra were obtained on either a Varian VXR-300 or VXR-400 nuclear magnetic resonance spectrometer.